[sdiy] Boards for a parametric EQ?

[Andre Majorel]

On 2008-09-10 17:41 -0400, Robert Lorentz wrote:

> I have been looking into building my own parametric EQ, looks like the
> best route is to use the BP output of a SVF.  To build one EQ would be
> like 3-5 of these filters, possibly with different component values to
> zero in on a certain frequency range.  Our beloved resonance would not
> have to make an appearance for this..
> 
> Does anyone have boards for sale of a simple design for this?  Would
> anyone have interest in buying some of these if I did a run of them?
> (seems like an ideal candidate to cut boards of for DIY purposes)

No PCB but here's a schematic (about halfway down the page) :

  http://www.ethanwiner.com/spectrum.html

One problem with equalisers is sourcing the pots. I have a
Rocktron here that uses dual gang reverse log (!) pots for the
frequency control. Ethan specifies dual gang linear for his but I
suspect that is not the right law. Also, in real life dual gang
pots, the tracks are poorly matched, which must put an upper limit
on the Q.

In the light of this, I'm thinking you might get better results
for less money and trouble by using voltage control.

I understand Jürgen Haible plans to clone the Moog parametric EQ
at some point.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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